Submerged arc welding method and flux cored wire for use in same

ABSTRACT

A flux cored wire for submerged arc welding is formed of a tubular wire of carbon steel or low alloy steel the hollow of which is filled with flux comprising, in mixture, highly basic slag forming ingredient, deoxidizing ingredient, denitrifying ingredient, desulphurizing ingredient, highly toughening ingredient, and working property improving ingredient in a suitable composition.

United States Patent 1 [111 3,868,487

Ito et a1. Feb. 25, 1975 [5 SUBMERGED ARC WELDING METHOD 92,522 \sNiicgx 1 mit gi ag CORED WIRE FOR USE IN 3,493,713 2/1970 Johnson 21 /73 X 3,701,444 10/1972 Clement et a1. 219/146 [75] Inventors: Yoshinori Ito, Nishinomiya; Mutsuo 3.702390 11/1972 Blake et 211.. 219/146 Nakanishi, Amagasaki both of Nakabayashl Japan Primary Examiner-J. V. Truhe [73] Asslgnee. gumkltonlio Metal Industries, Ltd., Assistant Examiner N D. Herkamp Sa apan Attorney, Agent, or Firm-Kurt Kelman [22] Filed: Feb. 5, 1974 21 Appl. NO.Z 440,128 [57] ABSTRACT A flux cored wire for submerged arc welding is formed of a tubular wire of carbon steel or low alloy steel the c i 219/73 i g g ho11ow of which is filled with flux comprising, in mixtum, highly basic g forming ingredient deoxidizing [581 Field of Search 148/24 219/73 146 ingredient, denitrifying ingredient, desulphurizing ingredient, highly toughening ingredient, and working [56] g g' g gif property improving ingredient in a suitable composition.

2697.159 12/1954 Donahey 148/26 X 3,303,323 2/1967 C1aussen.... 7 Clams, 1 Dmwmg Flgu" (209 COMPARATIVE) I 9 2 I G 1 LL] 1 [D PATENIEDFEB 2 5 ms BEAD WIDTH (mm) (209 COMPARATIVE) SUBMERGED ARC WELDING METHOD AND FLUX CORED WIRE FOR USE IN SAME BACKGROUND OF THE INVENTION The present invention relates to a submerged arc welding method of carbon steel and low alloy steel and a flux cored wire for use in said method.

In submerged arc welding of steel, there is a need for high efficiency and high speed in welding, and in reply to the need multiple electrode high speed welding and large heat input welding are used. Another need in the art is toughening of deposited metal. Although many attempts have been made to satisfy these two needs, none of them has been entirely successful in satisfying them simultaneously.

For example, by making the composition of the welding flux strongly basic, oxygen content of the deposited metal is reduced to improve the Charpy impact characteristic of the deposited metal zone, to thereby attain the toughening of the deposited metal. However, when such a strong basic flux is used, arc is made unstable to drastically decrease the weld working property, to thereby make the high speed welding impossible.

While such an attempt to add highly toughening elements, for example, molybdenum and nickel, to the deposited metal zone can improve the Charpy impact characteristic of such zone, it has a few disadvantages such that it is difficult to drastically improve the toughness and to properly regulate the strength that tends to increase too acutely. Further, the improvement in toughness of the deposited metal can be attained to a certain extent also by increasing the cooling rate of the weld zone owing to decrease in the amount of welding heat input. However, this method has a disadvantage that welding efficiency is considerably reduced.

Heretofore, it has been known to use a flux cored wire in submerged arc welding. The heretofore known flux cored wire comprised a hoop of carbon steel or low alloy steel having a welding flux and alloying elements filled therewithin. Such prior art flux cored wire, however, has very limited uses such, for example, as for adding high alloy compositions to weld metal as in buildup welding of stainless steel, because composite wire has problems in manufacture and in weld working property and that such flux cored wire can be sufficiently replaced by solidwire in practical uses.

In the case where a high toughness is required, addition of active alloying elements, such as Ti, Al, B, is indispensable. However, solid wire cannot provide such required active elements sufficiently since solid wire is oxidated when manufactured and, does not retain sufficient activity until welding. Accordingly, it cannot attain high toughness. However, the active elements can be freely added by flux cored wire since the manufacture of the flux cored wire includes no melting step.

Even when the flux cored wire is used, however, the desired high toughness cannot be attained unless suitably selected elements are added as the filling materials.

Heretofore, accordingly, the prior art flux cored wire was used mainly for the purposes such, for example, as 'to adding alloying elements in large amount and to improve the working property but has never been used for attaining high toughness.

SUMMARY OF THE INVENTION Accordingly, it is the object of this invention to provide a new submerged arc welding method for toughening the deposited metal and improving the weld working property and to provide also a flux cored wire for use in such method.

It is the characteristic feature of the submerged arc welding method according to the present invention to use in the submerged arc welding a flux cored wire including therein as the filling flux a high basic slag forming composition, deoxidizing agent, denitrifying agent, and high toughening elements in combination with a fused-type or bond-type flux. The filling flux used in the present method will be described hereinunder in more detail. In the method according to the present invention, submerged arc welding is carried out using the flux cored wire, formed by enclosing the filling flux according to the present invention with a hoop material of carbon steel or low alloy steel, as the welding electrode in combination with a fused-type or bond-type flux.

The submerged arc welding method is carried into practice preferably in the following forms:

1. Single Electrode Method Welding is carried out using the flux cored wire in combination with a fused-type or bond-type flux.

2. Multiple Electrode Method Flux cored wire is used for all the welding electrodes in combination with the fused-type or bond-type flux, or, the flux cored wire is used for only one or two of the multiple of electrodes the balance thereof being solid wires in combination with the fused-type or bond-type flux.

3. Water Cooling Submerged Arc Welding Method (Single Electrode and Multiple Electrodes) Submerged arc welding is carried out with the underside of the bead cooled by water to increase the cooling rate of the weld zone.

The present invention contemplates to use the flux cored wire for these forms of submerged arc welding. To this end, the compositions of the filling flux of the flux cored wire must be adjusted according to the form of welding method described above. For example, in two-electrode method, when a flux cored wire is used for an electrode and a solid wire for the other electrode, the compositions of the filling flux of the flux cored wire must be used in larger quantity than in the case where both electrodes are flux cored wires.

The filling flux of the flux cored wire according to the present invention comprises, in suitable combination, high basicslag forming composition, deoxidizing composition, denitrifying composition, desulphurizing composition, high toughening composition, and working property improving composition.

The hoop material of the flux cored wire according to the present invention is generally made of such material as carbon steel or low alloy steel. The material for the hoop should be selected according to the compositions of the welding and including fluxes used in combination to obtain the characteristics required in the weld zone. In the present invention, carbon steel or low alloy steel having the following composition is used: 001 0.10% C, trace 0.3% Si, trace 1.5% Mn, 0 1.5% Mo, 0 3.0% Ni, and the balance iron.

In the flux cored wire according to the present invention, it is preferable that the flux ratio (weight of including flux/weight of hoop material) X l00(%)) is in the range between 12 and 30 percent in view of the forms of submerged arc welding, welding flux used in combination therewith and production thereof. When the flux ratio is 12 percent or less, the increase in thickness owing to the increase in weight of the hoop material makes the forming thereof difficult. On the other according to the present invention includes a large amount of strong basic slag forming compositions as the including flux and, accordingly, the welding flux to be used in combination therewith canwell be neutral or hand, wh n th flllX ratio is 30 Percent mOre, the 5 weak basic, the present invention has an advantage that crease 1n the amount of fllllng flux and the decrease 1n th is no decr ase in weld working property. This is thwkqess Owmg to t e decrease In welght of p possible only when the flux is included within the flux' materlal make the filling of the flux and the forming of Cored wire hoop lmposslble- Genfaranyi F matenal P the In the present invention, the filling flux containing a thickness of 02 0.5 mm 1s used 1n the productlon of large amount f l ium fluoride (CaF is u d t the 1100? I duce the oxygen content of the deposited metal, and combmatlons h finmg fluxes and P mammals the elements aluminum (Al), titanium (Ti) and boron n varlous composrtlons of the flux cored wlre accord- (B) are added to strengthen the deoxidization and m mg to the present lnventlon are shown 1n Table 1. effect the denitrificatibm Table 1 Item Hoop Material (A) (wt%) Num- C Si Mn Mo Ni Fe her 100 Carbon Steel. or Low Alloy Steel 200 0.01-0.10 0-0.3 0-1.5 0-1.5 0-3.0 Balance 300 Carbon Steel, or Low Alloy Steel 400 Carbon Steel, or Low Alloy Steel 500 Carbon Steel, or Low Alloy Steel 600 0.01-0.10 0-0.3 0-1.5 0-1.5 0-3.0 Balance 700 Carbon Steel, or Low Alloy Steel I 800 0.01-0.10 0-0.3 0-1.5 0-15 0-30 Balance Filling Flux (B) (wt%) Flux Item Ratio Num- CaF Al Ti Mo B Ni Mn Fe Others B/A(%) bcr 100 25-98 01-25 0.8- 0.8-15 0.02-0.50 0-25 0-15 0-70 12-30 200 -98 0.1-2.5 0.8-15 0.8-l5 002-050 0-25 0-15 0-70 12-30 300 25-98 0.1-2.0 0.8-4.0 0.02-0.2 0-60 12-30 400 25-9s 0.1-2.0 0.8-4.0 0.8-l0 0.02-02 15-15 0-15 0-60 si 0-25 12-30 500 25-95 0-2.5 0.8-15 0-15 0-25 0-15 0-l0 Se, La, CeF 12-30 005- 600 25-95 0-2.5 0.8-15 0-15 0-25 0-15 0-10 se. La, CeF 12-30 ISO-0.5

0.05-30 Bal- Se 0-2.5 700 25-95 01-25 0.8-15 08-15 0.02-0 5 0-25 ance ceoa ilrocet 12-30 CaCO 2-20 Bal- Se 02.5 800 25-95 01-25 0.8-15 0.8-i5 0.02-0.5 0-25 ance CeO6or0CeF 12-30 CaCO 2-20 The reasons for defining the chemical compositions of the flux cored wires as shown in Table I will now be described.

i. Flux Cored Wires Nos. 100 and 200 Calcium fluoride (CaF in the fillingflux is to make the slag formed in the welding strongly basic to thereby reduce the oxygen content of the deposited metal. Since the strong basic slag formed by the filling flux of this flux cored wire is formed only locally in the neighborhood of the molten pool, the use of this flux cored wire can not only improve drastically the working property as compared to the use of the known solid wire where the entire welding flux is basic and the molten pool is covered by the strong basic slag but also reduce the oxygen content of the deposited metal to the level substantially the same as in the case where-the known solid wire is used in combination with the strong basic welding flux. Thus,'the use of solid wire in combination with strong basic welding flux results in the decrease in working property. However, since the flux cored, wire Since these additive compositions are added from the flux cored wire directly to the molten pool, the reduction in yield owing to, as in the solid wire, oxidization in the arc and floating from the molten metal can be prevented. However. in order that these deoxidizing and denitrifying agents can function effectively, it is necessary to reduce the oxygen content of the molten metal by addition of calcium fluoride, namely by coaction with calcium fluoride, thereby improving the toughness of the deposited metal.

In this invention, high toughening alloying elements such as molybdenum (Mo) and nickel (Ni) are added to improve the structure of the deposited metal simultaneously to improve the toughness of the deposited metal. These elements, molybdenum and nickel, improve the hardenability of the deposited metal, overlap the hardenability improving effect of boron added si- :multaneously, restrain the formation of pro-eutectoid ferrite of the deposited metal, and further improve the toughness of the deposited metal. Molybdenum and nickel may be added from the hoop material to the deposited metal.

Thus, the various effects achieved by the filling flux compositions of the flux cored wire according to the present invention, such as deoxidizing and denitrifying high toughening, improving the structure, and restraining the pro-eutectoid ferrite, become more helpful in improvement of toughness of the deposited metal by virtue of the overlapping action of these compositions.

The reasons for limiting the compositions of the present invention will now be described.

Calcium fluoride, as described hereinabove, makes the welding slag strong basic and reduces the oxygen dissolution in the molten metal. In order to make the other deoxidizing and denitrifying agents function effectively, the content of calcium fluoride of 25 percent or more is necessary. However, the upper limit of the calcium fluoride content is limited by the amount of addition of other compositions.

Titanium (Ti) and aluminum (Al) act as deoxidizing and denitrifying agents and serve to increase the toughness of the deposited metal. However, when the adding amount of aluminum is 2.5 percent or more, there is a tendency that SiO in the slag is reduced and silicon amount is increased, to thereby decrease the toughness. On the other hand, the addition of aluminum in 0.1 percent or less has no effect to improve the toughness. This confirms, accordingly, that the aluminum addition in the amount of 0.1 2.5 percent is preferable. When aluminum is added in the forms such as A1 0 and A11 the desired effect is not sufficiently obtained. Accordingly, it is essential that aluminum is added in the form of a metallic aluminum. Titanium addition is limited to 0.8 15 percent in view of the facts that the optimum yielding of Ti in the deposited metal is 0.04 percent, the Ti addition in 15 percent or more increases the silicon amount in the deposited metal to thereby decrease the toughness, and the Ti addition in 0.8 percent or less fails to provide the desired toughness owing to the shortage in titanium nitride.

Boron serves to increase the degrees of deoxidization and denitrification in the deposited metal, improve the structure of the deposited metal, restrain the formation of pro-eutectoid ferrite in the deposited metal, and induces fine grain formation of ferrite. However, .the boron addition in 0.02 percent or less the formation of pro-eutectoid ferrite in the deposited metal is not restrained and, accordingly there is no effect of improvement in toughness. On the other hand, the boron addition in 0.5 percent or more will increase the boron amount in the deposited metal to thereby cause the cracking of the deposited metal.

Nickel (Ni) and molybdenum (Mo) are added for adjusting the toughness and strength since they increase both the toughness and strength of the deposited metal. However, the nickel addition in percent or more is not desirable since the toughness improving effect is saturated and the cost is increased. When the molybdenum addition is 15 percent or more, the toughness improving effect is saturated, the strength is increased to 'more than desirable, and the cost is increased. And the molybdenum addition in 0.8 percent or less there is no effect to improve the toughness.

While manganese (Mn) is also added to improve the toughness, the addition thereof in 15 percent or more increases the silicon amount in the deposited metal to thereby decrease the toughness. However, these may be contained in the hoop material.

ii. Flux Cored Wires Nos. 300 and 400 In these flux cored wires, calcium fluoride (CaF in 25 98 percent is used in the filling flux. The adding amount of calcium fluoride is limited to 25 98 percent, since, when 25 percent or lower, the oxygen amount in the weld metal is not different from that in the case where the common welding wire is used and the effect characteristic of the present invention is not obtained.

Further, the flux cored wire according to the present invention contains Al, Ti and B for deoxidization and denitrification of the weld metal. Since these elements are added as the flux cored wire directly into the weld metal, there is very little oxidization in the arc and floating from the molten pool, and they directly and effectively function for deoxidization and denitrification. In order that these deoxidizing and denitrifying agents function effectively, it is essential that the oxygen content of the weld metal is decreased to a certain degree. From this respect, the effect of using them jointly with CaF is great.

The addition of Al is considerably effective in reducing the impact test fracture transition temperature of the weld metal zone, and the addition of Ti, B is effective in improving the impact test absorbed energy and reducing the fraction transition temperature. Accordingly, as a result of the composite addition of these three alloying elements, the toughness of the weld metal zone is drastically improved. However, when Ti and A1 are added in large amounts, Si0 in the slag is reduced to increase the Si content in the weld metal to thereby reduce the toughness. Accordingly, it is not preferable that the amount of Al addition is 2.0 percent and the amount of Ti addition is 4.0 percent or more. And also, when Al is 0.10 percent or less and Ti is 0.8 percent or less, the improvement in toughness cannot be anticipated.

B deoxidizes and denitrifles the weld metal. B contained in the weld metal refines the structure to thereby increase the toughness. However, the B addition in 0.20 percent or more tends to cause cracking and, on the other hand, the addition thereof in 0.02 percent or less produces no effect.

The armoring tubular body of the flux cored welding wire according to the present invention is normally formed of carbon steel or low alloy steel hoop material. When the mechanical strength required in the weld zone is higher than the use and object of the material of base metal and the welded structure, one or two or more of C 0.01 0.10 percent, Si 0.30 percent or less, Mn 2.0 percent or less, M0 0.2 1.0 percent, and Ni 0.5 3.0 percent are added to the composite welding wire, namely the hoop material or including flux, to thereby improve both the toughness and strength. in such case, the object can be achieved with good yielding by using low alloy material suitable for said object as the hoop material which will serve as the armor or by adding to the including flux said alloying elements in simple substance or alloyed iron such as Fe-Si, Fe- Mn, and Fe-Mo in granular form.

iii. Flux Cored Wires Nos. 500 and 600 Calcium fluoride (CaF in the filling flux makes the slag formed in welding strong basic to thereby reduce the oxygen content of the weld metal and prevents tita-' nium (Ti), selenium (Se), lanthanum-cerium (La-Ce),

cerium fluoride (CeF and other filling compositions from oxidization to thereby make these compositions to effectively function. Calcium fluoride also serves to improve the toughness of the weld metal by reducing the oxygen content of the weld metal.

Metallic aluminum, titanium and boron strengthen the deoxidization, fixes nitrogen in the weld metal, refines the structure of the weld metal, and restrains the formation of the pro-eutectoid ferrite.

Selenium (Se), lanthanum-cerium (La-Ce) and cerium fluoride (CeF serve as desulfurizing agents to desulfurize by fixing sulfur as sulfides of selenium, lanthanum, and cerium to thereby double the toughness of the weld metal. Thus, the filling flux of the flux cored wire according to the present invention drastically improves the toughness of the weld metal by the multiplication effect of the deoxidizing effect, the refining of the structure, the restraining of the pro-eutectoid ferrite, and the desulfurizing effect.

CaF is added to make the welding slag strong basic thereby reducing the oxygen content in the weld metal. It is necessary to use the including flux containing 25 percent or more CaF in order to make the other deoxidizing, denitrifying and desulfurizing agents in the including flux to effectively function. Since Se, La-Ce, and CeF are desulfurizing agents and the addition of them in too large amount tends to be detrimental to the toughness, the upper limit of the amount of theiraddition is set to 3 percent.

Other compositions are as described hereinbefore.

iv. Flux Cored Wires Nos. 700 and 800 CaF in the filling flux is added to make the slag formed in welding strong basic and to reduce the oxythe restraining the pro-eutectoid ferrite, and the desulfurizing effect. On the other hand, the filling flux thus produced has, when compared with solid wires, disadvantages such that the bead width is smaller, there are more undercut and necking (arc off), and working property is inferior. This is attributed to the facts that the reignition voltage in the AC arc is very high, the possibility of are off (no arc is generated when the reignition voltage is higher than the no-load voltage) is large, the bead form is damaged, negative fluorine ions (F') are generated in the arc space from calcium carbonate (CaCO in the flux cored wire, neutralization is forwarded, and the potential gradient is increased.

It has been found, however, that when 2 20 percent of CaCO is added to the filling flux, good bead form having a large width is obtained and the working property of the composite wire can be improved identical to that of the solid wire.

Thus, Ca having a low ionization potential is presumably a main cause for capability of improving the bead form by adding CaCO to the flux cored wire having high toughness. During arc ignition with AC arc, ions such as CA and F are considered to be present in the arc space. At the time of arc extinction whereat the electric current becomes zero phase, the ions become unstable and are neutralized. In the wire added with 2 20% CaCO however, since there is large amount of Ca, even when the reverse load is applied ionization easily takes place as Ca Ca and, therefore, even when turning to are discharge since no great reignition potential is required the arc is considered to become stable and the bead form can be improved. In this case, however, when the adding amount of CaCO becomes 20 percent or more by wire weight percent, a large gen content of the P q P thereby improving amount of unstable CO gas is generated by the welding the toughness To thls It nicessaryfhat CaFz reaction and sputtering is caused, to thereby damage gg g m 25 R a lizllgtalhc g i are the bead form. This phenomenon affects more ada e g g g s f; versely the welding of the rearward electrodes in the l an pefrcem to Smingt wt 6 1' multi-electrode welding. Since the addition in 2 perzation, to for n1trogen 1n the deposited metal, to refine 40 cent or less does not provide the effects Such as Stabi the structure of the deposited metal, and to restrain the Zing of are the adding amount of CaCOa is set to 2 formation of pro-eutectoid ferrite. Se, CeO or CeF 20 percent serves as desulfurizing agent for removing sulfur by fixing it as sulfide of Se or Ce and for doubling the tough- BRIEF DESCRIPTION OF THE DRAWING of p l metal- The sole drawing is a graph showing the relation be- Slflce N1 and M0 Increase both the toughness and tween the percentage of calcium carbonate and the strength of the deposited metal, they are added for adv bead width justing not only the toughness but also the strength. To p this end, they are added in the amount: NiO 25 per- DESCRIPTION OF THE PREFERRED cent, M0 0.8 15 percent. They may be added in the EMBODIMENTS 'hoop material. Thus, the filling flux of the flux cored wire added with CaF and metal elements improves the f f gg g gg i s figg z g i present Inventoughness of the deposited metal by the multiplication of the deoxidizing effect, the refining of the structure, EXAMPLE 1 Table 2 Chemical Composition of Test Sample (wt%) Thick- Num- C Si Mn P S V Nb ness ber Table 3 Chemical Composition of Flux Cored Wirc (Flux Ratio 15%) Num- Hoop Material (wt%) Filling Flux (wt t) her C Si Mn P s cm Al Ti Mo 8 Ni Mn Fe 201 0.06 0.32 0.005 0.010 04 0.8 3.2 4.0 0.12 3.0 7.2 Balance 202 do. do. do. do. do. do. do. do. do. do.

Table 3 Continued Chemical Composition of Flux Cored Wire (Flux Ratio 15%) Num- Hoop Material (wt%) Filling Flux (wt%) ber C Si Mn P S CaF Al Ti Mo Ni Mn Fe 203 do. do. do. do. 80 do. do. 7.2 do. do. do. 204 do. do. do. do. 76 do. do. 4.0 0.08 8.0 do. 205 do. do. do. do. 76 do. do. do. 0.16 8 do.

Table 4 Table 6 Welding Conditions Impact Characteristics of Deposited Metal Zone (JlS-No. 4 Charpy Value KG-m) Number of One layer welding each Welding Layer at front and back Number -10C -C Method of Welding Flux cored wire two electrode 2m (941) (6'2) Submerged Weldmg 202 6.8, 6.0. 5.5 (0.1) 5.7. 4.8. 4.9 (5.1)

Combined Flux Fused type basic flux 20 203 129, .7, 9.0. 10.9 (9.9)

204 9.4, 9.8. 8,6 (9.3) 6.4. 6.1, 5.7 (6.1) Ammm 50000 mm 205 9.9, 10.2, 7.2 9.1 9.2, 7.6, 8.3 (8.4)

l 4 1' A 1 A We dmg Condition Forward 43 X1200 +Rearward 55 X700 EXAMPLE 2 welding Speed H0 cm/min Chemical Composition of Test Sample. Same as Table 2.

Table 7 Chemical Compositions of Flux Cored Wire and Solid Wire Composition of Flux Cored Wire (Flux Ratio 20%) Hoop Material (wt%) Filling Flux (wt%) C Si Mn P S CaF Al Ti M0 N1 Mn Composition of Solid Wire (wt%) C Si Mn P S Mo Cu Table 5 Table 8 Chemical Composition of Deposited Metal Zone (wt%) Welding Conditions Num- C Si Mn P S Ni Number of ber Welding Layer Method of Welding 202 0.08 0.42 1.29 0.015 0.010 Forward t od 203 0.08 0.42 1.33 0.014 0.010 Electmde 205 0.08 0.42 1.33 0.018 0.017 0.37 Combined Flux Num Mo V Nb Ti B ber Heat lnput Amount 201 0.18 0.043 0.012 0.042 0.002

Welding Condition 205 0.20 0.039 0.025 0.045 0.002 Welding Speed One layer welding each at front and back Flux cored wire (F) Solid wire A or B Fused type basic flux 50000 J/cm Forward 43"X1050"+Rcarward 45 X750 05 urn/min Table 9 Chemical Composition of Deposited Metal Zone (wt%) Forward Rearward Num- Electrode Electrode C Si Mn P S Ni ber (i) 206 A 0.09 0.45 v 1.35 0.016 0.011 0.50

(ii) 206 B 0.08 0.40 1.27 0.014 0.010 0.43

Forward Rearward Num- Electrode Electrode Mo V Nb Ti B her Table 10 Table 14 Impact Characteristics of Deposited Metal Zone impact Characteristics of Deposited Metal Zone (HS-No.4 Charpy Value Kg-m) (JlS-No.4 Charpy Value Kg-m) Numl0C 20C No. -C C her EXAMPLE 3 (Water Cool Submerged Arc Welding) Chemical Composition of Test Sample: Same as 30 Comparative Example (The conventional solid wire two electrodes method) Chemical Composition of Test Sample: Same as Table 2. Table 2.

Table l 1 Chemical Compositions of Flux Cored Wire (Flux Ratio 20) Hoop Material (wt%) Including Flux (wt%) Num- C Si Mn P S CaF Al Ti Mo B Ni Mn ber 207 0.06 Trace 0.3 0.012 0.010 76 0.8 3.2 4.0 0.12 8.0 7.2

Table 12 Table 15 Chemical Compositions of Solid Wire (wt%) Welding Conditions Num- C Si Mn P S Cu Mo Number of One layer welding each at her Welding Layer front and back i C 0.12 1.49 0.018 0.017 0.10 0.51 Welding Method Flux cored wire two electrodes water cool submerged arc welding method T bl 16 Combined Flux Fused type basic flux welding Conditions Heat Input Amount 5000b Hem Welding Method Two electrodes submerged arc welding Number of One layer welding each at front and Water Cooling Water cool the backside of the head weldmg Layer back during 1; Combined Flux Fused type basic flux Welding Condition Forward 43" 1200-+Rearward s5" 70n-' 5000 Welding Condition Forward 38"Xl200"+Rearward 43"X750 Welding Speed cm/min Welding p d 110 /m Table 13 Chemical Composition of Deposited Metal Zone (wt%) Numc Si Mn P s Ni Mo v Nb Ti B her Table 17 Chemical Composition of Deposited Metal Zone (WW/r) Num- C Si Mn P S Mo V Nb ber Table 18 Impact Characteristics of Deposited Metal Zone (HS-No.4 Charpy Value Kg-m) Num- C -c 20C 40C ber According to the present invention, as is obvious Table 2l from the above descriptions, the value of absorbed energy of the impact test in various composition systems Welding Conditions are drastically improved and the brittle fracture is conh d d 1 Using welding w11'e of Usmg welding siderably lessened compared w1t the epo s1te meta this invemion wire of of the case where the convent1onal sol1d wlre is used. prior art And, as 15 obv1ous from the weldmg condltlons 1n the Bevel form of Test 500v have] Same Examples, the weld workmg property 1s substant1ally sampie the same as in the conventional art in sp1te of the fact that a large amount of high baslc composmons are welding Method Two electrodessubmergcd S e added to the filling flux 1ncluded in the flux cored w1re. arc weldmg EXAMPLE 4 Combined Flux Bond flux suitable for same To the test sample (welding base metal) having the SMSO chemical composition shown in Table 19 was welded a welding wire according to the present invention as welding Hem P 001100 mules/Cm Same shown in Table 20 by submerged arc welding under the welding condition shown in Table 21. The results of Welding Condition Forward "xs00 same measurements of the impact value and chemical com- 40 Rcarwmd X620 positions of the weld metal zone thus welded are shown w M S d 40 m/min am I CC C I C In Tables 22 and 23. L p

Table 19 Chemical Composition of the Test Sample (wt%) Num- C Si Mn P S Nb Thickness her Table 20 Chemical Compositions of the Flux Cored Wire and the Solid Wire Hoop Material (A) (wt%) Filling Flux (B) (wt%) Flux Number C Si Mn P S CaF: Al Ti Fe Ratio% 301 This 0.00 0.40 0.012 0.015. 0.0 2.0 0.12 Balance 15 Invention D Prior Table 22 Impact Characteristics of Deposited Metal Zone (HS-No.4 Charpy Value Kg-m) I Test Temperature 0C C Using Flux Cored Wire (301)0fthis 16.6 17.8 18.5 (17.6) 16.0 15.8 14.5 (15.4)

Invention Using Welding Wire (D) of Prior Art 6.0 6.4 6.8 (6.4) 4.5 4.3 4.4 (4.4)

Parenthesized values indicate averages.

Table 23 Chemical Compositions of Deposited Metal Zone (wt%) Num- C Si Mn P S Mo Nb Ti B 501 her EXAMPLE 5 Table 26 Welding Conditions Using Using To the three kinds of test samples having the chemlweldipg wk? of welding wire cal compositions shown in Table 24 was welded a flux Bevel form of cored wire according to the present invention as shown Test Sample X bevel same Welding Method Two electrodes submerged in Table 25 by submerged arc welding under the weld- Method arc welding same I Combined mg condition shown in Table 26. The results of meas- Flux I Fused yp basic flux same Welding Heat urements of the im act value and chemical com osi- 1 p p Welding Forward 43 X 1200* 1 l' A trons of the weld metal zone thus welded are shown in $313? 55 X 700 Table 27 and 28. Speed 110 em/min same Table 24 Chemical Compositions of the Test Samples (wt%) Number C Si Mn P S V Nb Thickness TABLE 25.( 11EM1(AL (.UMlOSlllONS OF THE FLUX (.ORED W111i) ANl) SOLID WIRE 1100p material (A) (wl. percenl) Filling flux (B) (wt. percent.) Flux ratio (percent). Number C Mn Mo 1 S Ct] CaF; Al Ti M0 B Ni Mn Fe B/A 401 (thisinvention)..." 0.06 0.32 .0... 0.005 0.010 0.0 2.0 2.5 0.08 5.0 4.5 Balance 20 E (prior art) 0.12 1.50 0.50 0.018 0.017 0. 10

Table 27 impact Characteristics of Deposited Metal Zone (HS-No.4 Charpy Value Kgm) Test Temperature 0C lOC Using Welding Wire 4010f 10.2 9.2 8.2 (9.2) 9.8 8.8 8.8 (9.1) this Invention Test Sample Using Prior art 5.3 5.1 5.1 (5.2) 40 4.1 4.0 (4.0) 3.8 4.0

(111) Welding Wire E Test Using Welding Sample Wire (401) of (1V) this Invention Test Using Welding Sample Wire (401) of (V) this lnvention Parunthesized values indicate averages.

TABLE 28.CIIEMICAL COMPOSITIONS OF DEPOSITED METAL 7.0m: (W'1.'1ERCEN'1) o si Mn 1* s Ni Mo v N1) 'li n .u a

Test sample: (III):

Using welding wire (401) 01 this invention 0.08 0.41 1.33 0. 017 0.015 0. 32 0.18 0.013 0. 01:! 0. 01'. 0. 003 0.010 Using prior artwe1dingwire(E) 0.00 0. -10 1.30 0.010 0. 011 0. 20 0. 040 0.010 0. 000 0.0101 (1V) (using welding wire (401) olthis invention) 0. 0.40 1.33 0.017 0. 010 0.18 0. 22 0.020 0.007 0. 051 0.0051 0. 01'. (V) (using welding wire (401) of this invention) 0.00 0.30 1. 30 0.017 0. 018 0.18 0. 22 0. 005 0.011 0. 0111 0.0031 0. 01'.

As is obvious from the above Examples, in the sub- Table 31 merged arc welding using the flux cored wire according to the present invention, toughness, especially low tem- COmPamm perature impact value of the weld metal zone is drasti- Number C Si Mn P S cally improved as high as substantially double those in the case where the conventional welding wire is used. F 046 1007 M14 Table 32 As described above, the present invention is industriwelding Conditions ally advantageous 1n that the structure of welded metal zone having high toughness and reliability can be made without reducing the weld working property. The advantage of the present invention is excellent particularly in weldability of high tension steel plate in shipbuilding and line pipe in a cold district.

EXAMPLE 6 Table 29 Chemical Composition of the Test Sample (wt%) Welding Method Number of Welding Layer Combined Flux Three electrodes submerged arc welding One layer welding Burning type flux added with Mo Heat Input Amount 260.000 Joules/cm Num- C Si Mn P S Nb Thickness ber Table Chemical Compositions of the Flux Cored Wire (Flux Ratio 20%) Hoop Material (wt%) Filling Flux (wt%) Num- C Si Mn P i S CaF Ti B Fe Se La-Ce CeF her 601 0.06 trace 0.3 0.0l 0.01 96 2.0 0.1 Balance 1 0 602 do. do. do. do. do. 96 do. do. do. 1.0 603 do. do. do. do. do. 94 do. do. do. 3.0

Table 33 Chemical Compositions of Deposited Metal Zone (wt%) Num- C Si Mn P S Ni Mo Nb Ti B Se Ce her Table 34 Impact Characteristics of Deposited Metal Zone (HS-No.4 Charpy Value Kg-m) Number C C 40C EXAMPLE 7 Table Chemical Composition of the Test Sample (wt%) Number C Si Mn P S V Nb Thickness (Vll) 0.08 0.31 1.33 0.016 0.008 0.06 0.03 20 Table 36 Chemical Composition of the Flux Cored Wire (Flux Ratio 19%) Num- Hoop Material (wt%) Filling Flux (wt%) ber C Si Mn P S CaF, Al Ti Mo B Ni Se Fe 604 0.06 trace 0.3 0.01 0.01 79 0.6 2.5 7 0.15 5 l8 Balance Table 37 Table 39 Welding Condition 40 Welding Method One layer welding each at front and back impact Characteristics of Deposited Metal Zone submerged arc welding with two electrodes (HS-No.4 Charpy Value Kg-m) Combined Flux Melting type neutral Flux Welding input heat 55000 .I/cm Number 0C l0C 20C 40C C Welding Condition 43V l l30A+45VX750A Welding Speed cm/min 45 604 l 1.7 10.9 9.5 7.0 4.9

EXAMPLE 8 Table 38 Chemical Composition of Deposited Metal Zone Num- C Si Mn S Ni Mo V Ti B Se ber Table 40 Chemical Composition of the Test Sample (wt%) Number C Si Mn P S V Nb Cu Cr Thickness Table 41 7 Hoop Material (wt%) Filling Flux (wt%) Number C Si Mn P S CaF Al Ti Mo B Ni Fe CaCO;

801 0.06 trace 0.3 0.01 0.01' 68.7 0.8 4.8 8.2 0.2 13.7 Balance 3.4

802 do. do. do. do. do. 66.4 do, 4.7 8.0 do. 13.2 do. 66

803 do. do. do. do. do. 64.3 do. 4.5 7.7 do. 12.9 do, 9.6

209 (Comparison) do. do. do. do. do. 71.2 0.9 5.0 8.5 do. 14.2 do.

Table 42 Solid Wire Used in Rearward (wt%) Num- C Si Mn P 8 Cu Mo her (Note) G wire was used as the rearward wire of the two electrodes.

Table 43 essentially of 0.1-0.l0%C, trace 0.30% Si, trace 1.5% Mn, up to 1.5%Mo, up to 3.0%Ni, and the bal- Welding Conditions ance Fe, all percentage by weight.

. 'r i Welding Method Two electrodes submerged arc welding 3 A flux cored e for Submerged arc welding Wh ch (Forward Cored Wire, Rearward Solid Wire) Welding lnput Heat 48,000 l/cm Welding Condition Forward 42V 1 150A+Rearward SOVXSOOA Welding Speed 1 1O cm/min Table 44 Impact Characteristics of Deposited Metal Zone (.llS-No. 4 Charpy Value Kg-m) Regarding the working property, the variation in bead width to accompany the variation in percentage of CaCO is illustrated as in the attached drawing considering that the arc is stable when the bead width is large.

We claim:

1. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 2598%CaF 0.1-25%Al, 0.8-15%Ti, 0.02-0.5%B, 0.8-15%Mo, 025%Ni, O-l5%Mn, and O-70%Fe, all percentages by weight, the percentage of total weight of flux to weight of sheath material being l230%.

2. The flux cored wire for submerged arc welding as set forth in'claim 1 wherein the sheath material consists comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 2598%CaF 0.10-2.0%Al, 0.84.0%Ti, 0.02-0.2%B, and 060%Fe, all percentages by weight the percentage of total weight of flux to weight of sheath material being 12-30%.

4. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled withinthe sheath, said flux consisting essentially of 25-98%CaF 0.10-2.0%Al, O.84.0%Ti, 0.02-0.2%B, 0.810%Mo, and 1.5l5%Ni, all percentages by weight the percentage of total wieght of flux to weight of sheath material being 13-30%.

5. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 2598%CaF 0.815%Ti; 0.1-2.5%A1; 0.02-0.5%8; ODS-3.0% of at least one member of the group consisting of Se, La-Ce, and CeF and 0.8-15%Mo, all percentages by weight the percentage of total weight of flux to weight of sheath material being l230%.

6. The flux cored wire for submerged arc welding as set forth in claim 5 wherein the sheath material consists essentially of 0.01-0.10%C, trace 0.30%Si, trace 1.5% Mn, up to 1.5%Mo, up to 3.0%Ni, and the balance Fe all percentages by weight.

7. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 25-95%CaF 0.12.5%A1,0.8-15%Ti,0.8-l5%Mo,0.02-0.5%B and 225%CaCo all percentages by weight, the percentage of total weight of flux to weight of sheath material being l2-30%. 

1. A FLUX CORED WIRE FOR SUBMERGED ARC WELDING WHICH COMPRISES IN COMBINATION, A SHEATH FORMED OF CARBON STEEL OR LOW ALLOY STEEL, AND A FLUX FILLED WITHIN THE SHEATH, SAID FLUX CONSISTING ESSENTIALLY OF 25-98%CAF2, 0.1-25%A1, 0.8-15%TI, 0.02-0.5%B, 0.8-15%MO, 0-25%NI, 0-15%MN, AND 0-7%FE, ALL PERCENTAGES BY WEIGHT, THE PERCENTAGE OF TOTAL WEIGHT OF FLUX TO WEIGHT OF SHEATH MATERIALS BEING 12-30%.
 2. The flux cored wire for submerged arc welding as set forth in claim 1 wherein the sheath material consists essentially of 0.1-0.10%C, trace -0.30% Si, trace - 1.5% Mn, up to 1.5%Mo, up to 3.0%Ni, and the balance Fe, all percentage by weight.
 3. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 25-98%CaF2, 0.10-2.0%Al, 0.8-4.0%Ti, 0.02-0.2%B, and 0-60%Fe, all percentages by weight the percentage of total weight of flux to weight of sheath material being 12-30%.
 4. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 25-98%CaF2, 0.10-2.0%Al, 0.8-4.0%Ti, 0.02-0.2%B, 0.8-10%Mo, and 1.5-15%Ni, all percentages by weight the percentage of total wieght of flux to weight of sheath material being 13-30%.
 5. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 25-98%CaF2; 0.8-15%Ti; 0.1-2.5%Al; 0.02-0.5%B; 0.05-3.0% of at least one member of the group consisting of Se, La-Ce, and CeF3; and 0.8-15%Mo, all percentages by weight the percentage of total weight of flux to weight of sheath material being 12-30%.
 6. The flux cored wire for submerged arc welding as set forth in claim 5 wherein the sheath material consists essentially of 0.01-0.10%C, trace -0.30%Si, trace - 1.5% Mn, up to 1.5%Mo, up to 3.0%Ni, and the balance Fe all percentages by weight.
 7. A flux cored wire for submerged arc welding which comprises in combination, a sheath formed of carbon steel or low alloy steel, and a flux filled within the sheath, said flux consisting essentially of 25-95%CaF2, 0.1-2.5%Al, 0.8-15%Ti, 0.8-15%Mo, 0.02-0.5%B and 2-25%CaCo3 all percentages by weight, the percentage of total weight of flux to weight of sheath material being 12-30%. 